Habitat/ecology: "It is found along
streams, rivers, in low-lying areas subject to flooding, and in waste places.
It frequents roadsides, railway banks, small streams, and riverbanks, as well as
the edges of ponds and freshwater marshes and poorly managed or overgrazed
pastures. It cannot stand shading. The weed can grow on a wide range
of soils, from sands to heavy clays, and in a wide range of moisture supply.
On rich soils with high moisture and little competition from other plants, it
grows tall and luxurious, forming pure stands. In dry, poor soils, if the
seedlings have become established, the plant may grow to only a few cm in
height, persisting under drought, but still fruiting and setting seeds.
This ability to grow under a wide range of conditions results in a constant seed
supply if the plant is not controlled" (Holm et al., 1977; p. 480).
"An extensive root system and rapid growth make these plants strong competitors
with desirable forages and crops"
(Motooka et al., 2003).

"In Hawaii a common weed of low elevation, relatively dry, disturbed habitats" (Wagner et al., 1999; pp. 376-377). In Fiji, "occurring near sea level or at low elevations probably not exceeding 100 m as a naturalized weed in open places, cultivated areas, and grasslands, and along roadsides, sometimes locally abundant" (Smith, 1991; pp. 289-290).
In Australia, "riparian zones along river systems where it forms dense thickets.
Also invades grazing and cultivated lands, and seasonally wet areas" (Smith, 2002; pp. 67-68). "A weed of grazing land; the burrs are troublesome to livestock and the plants are harmful and even fatal if eaten" (Henty & Pritchard, 1975; p. 87).

Propagation: "The spiny fruit...adhere to wool, fur, clothing, hay bales, mud, etc. The fruits float and are readily dispersed by water. Fruits are also spread in contaminated pasture seed" (Smith, 2002; pp. 67-68).
"As is true of X. spinosum, the two seeds in the fruit...germinate at
different rates. The lower seed germinates more readily than the upper
seed, which has a seed coat of low permeability to oxygen. Both seeds show
dormancy, but the lower is less dormant than the upper" (Holm et al., 1977; p. 480).

Physical:
"Control measures should aim at preventing seed formation. Small plants
can be hand pulled or hoed. Prescribed burning is also effective if the
fire is hot enough" (Weber, 2003; p. 457). "Australian officials
have imposed strict quarantines to keep uninfested areas clear of this weed.
Small infestations can be effectively cleared by hand pulling or hoeing with
care to collect, remove and burn any burs. Controlled burning my also be
effective on larger areas" (Motooka et al., 2003).